GPS question

kevin47881

kevin47881

Final Approach
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GPS Approach question

Good day fellow POA'ers. While looking at this approach http://204.108.4.16/d-tpp/0712/05278R4.PDF a question came to mind that I'd like clarification on.

Let's assume you're on final in the soup and lose the GPS signal. The missed approach procedure directs you to hold at COYAP, which is a GPS way point. However, without GPS, you are unable to locate COYAP.

My initial thought is to fly above the MSA and contact the controlling agency for assistance with a different hold until another applicable IAP is determined. Of course, one can always return to another airport in VMC providing fuel and wx coverage are not an issue but that is not the case as the entire area is IMC.

Comments?
 
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I had a very similar experience. 1,8NM from the FAF the GPS lost all signal. I was in the soup, had just been handed off to the CTAF and now had no idea how to fly to a missed approach fix, and there were tall antennas to the right of my course. I immediately switched back to approach, advised them and asked for a vector, all the while hold my heading.
 
Just like any nav loss, DR it until you either contact someone who can give you an alternate procedure that you can navigate, although I wouldn't hesitate to climb to MSA if the missed approach procedure didn't take me above nearby terrain. I think in this case that the published holding altitude would work, though...it would appear* that the higher obstacles requiring the 2800-ft MSA are elsewhere within the 25-mile ring.

Fly safe!

David

*standard ignorance disclaimers apply, see dealer for details ;)
 
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I probably would have picked the ILS to start with since one is available. But, I would still have self-briefed on the VOR and GPS approaches while en-route just in case there was a last minute change.
 
I appreciate the comments so far...keep 'em coming.

Keep in mind I'm asking as my check ride is in about 2 weeks and I like to find "different" scenarios to challenge my thinking.
 
Hi Kevin,

I would apply power, start the missed procedure by climbing to 2300 on a 038 heading and contact approach control, in this case Chicago Center on 132.5 to report the missed approach, the equipment failure and request further instructions. Thence...

If asked to "Say intentions...", I would answer: "I want to fly direct IKK VOR and hold unless you can vector me for the ILS Rwy 4, LOC Rwy 4 or VOR Rwy 4 approach in that order of preference."

or,

If the problem is more than just a failure to receive a reliable GPS signal and I can't communicate with Chicago Center, I would squawk 7600 and turn towards the IKK VOR, continue the climb to 2700 feet (the highest of the two missed approach altitudes) and enter the hold.

After a couple of turns around the racetrack to regain my composure, check my underwear and pull the next approach plate, I would attempt the ILS Rwy 4, LOC Rwy 4 or VOR Rwy 4 approach in that order of preference depending on ground equipment availability and visibility and ceiling conditions.

Good luck in your checkride!
 
Since the MAP is just about colocated with the VOR, which is the holding point for the ILS4 I would fly runway heading, make the turn back to where you thought the VOR was (Ded Reckoning) climbing to 2700. Chicago has great radar coverage in that sector- they'll vector you above 1500.
 
Thank you very much for your insight Gil and Bruce.

Bruce - did you mean to type 2800 as oppossed to 2700?

Gil - why 2300 (granted there are no obstacles depicted above 1022) and not the MSA of 2700?

I'm not trying to be difficult but rather trying to dig deeper into your gray matter to determine WHY you would do what you stated.
 
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kevin47881 said:
Gil - why 2300 (granted there are no obstacles depicted above 1022) and not the MSA of 2700?
Click to expand...
Obviously I'm not Gil, but in this case, I'd probably use 2300 as well...the limited amount of DR you're going to have to do will likely keep you inside protected airspace for a reasonable amount of time. Even if it doesn't, 2300 still gives you 500 ft above the highest obstacle within the MSA's radius, and keep you from doing anything too unexpected with regard to ATC and other possible nearby aircraft.

Although I wouldn't tell anyone NOT to take the MSA if they felt the need. PIC is still in charge.

Fly safe!

David
 
As David stated, I would start my climb with 2,300 as an initial target altitude, the altitude of the missed approach procedure, expecting to contact Chicago Center almost immediately and certainly before flying 5 NM in the direction of the missed approach holding fix, in which case they would most certainly vector me.

On the other hand, without the assurance of being vectored by Chicago Center, I stated that I would turn towards the IKK VOR while climbing to 2,700. We're talking seconds here to decide one or the other.
 
Re: GPS Approach question

kevin47881 said:
Good day fellow POA'ers. While looking at this approach http://204.108.4.16/d-tpp/0712/05278R4.PDF a question came to mind that I'd like clarification on.

Let's assume you're on final in the soup and lose the GPS signal. The missed approach procedure directs you to hold at COYAP, which is a GPS way point. However, without GPS, you are unable to locate COYAP.
Click to expand...

A helpful thing to do when flying instruments is to make sure EVERY radio in your stack is doing something for you (even the ADF, if so equipped, can be helpful). In this case, you have a GPS approach and I'm going to guess you're navigating via GPS for the entire time even though you may be flying one of the published transitions from a VOR.

In that case, with my setup (G430 Nav/Com 1, Mac 1700 flip/flop Nav/Com 2), I'd probably tune the ILS into the 430 even if I was flying the GPS approach, and I'd have the on-field VOR tuned in to the other radio. Standby frequencies could be tuned into other VOR's (such as Pontiac in this example) off course for use in position-keeping.

If the radios are set up like that, when you lose GPS signal you could immediately revert to the ILS (FAC appears to be the same, final approach is 038 on both) and at least use that to navigate while you either fly to the missed approach procedure for the ILS (preferred), climb above MSA, or even finish by using the ILS if you absolutely need to. (Better have it pre-briefed!)
 
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